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Migrate pattern matching

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mejrs 2022-12-23 21:02:23 +01:00 • committed by David Tolnay
parent ef33072890
commit 31c20210b9
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GPG key ID: F9BA143B95FF6D82
35 changed files with 417 additions and 326 deletions
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166
compiler/rustc_mir_build/src/errors.rs
View file

@ -1,8 +1,11 @@
use crate::thir::pattern::deconstruct_pat::DeconstructedPat;
use crate::thir::pattern::MatchCheckCtxt;
use rustc_errors::Handler;
use rustc_errors::{
error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, MultiSpan,
error_code, AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
IntoDiagnostic, MultiSpan, SubdiagnosticMessage,
};
use rustc_hir::def::Res;
use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
use rustc_middle::thir::Pat;
use rustc_middle::ty::{self, Ty};
@ -677,7 +680,6 @@ pub struct OverlappingRangeEndpoints<'tcx> {
pub overlap: Overlap<'tcx>,
}
#[derive(Debug)]
#[derive(Subdiagnostic)]
#[label(mir_build_overlapping_range)]
pub struct Overlap<'tcx> {
@ -692,10 +694,158 @@ pub struct Overlap<'tcx> {
#[note]
pub(crate) struct NonExhaustiveOmittedPattern<'tcx> {
pub scrut_ty: Ty<'tcx>,
#[label]
pub uncovered: Span,
pub count: usize,
pub witness_1: Pat<'tcx>,
pub witness_2: Pat<'tcx>,
pub witness_3: Pat<'tcx>,
#[subdiagnostic]
pub uncovered: Uncovered<'tcx>,
}
#[derive(Subdiagnostic)]
#[label(mir_build_uncovered)]
pub(crate) struct Uncovered<'tcx> {
#[primary_span]
span: Span,
count: usize,
witness_1: Pat<'tcx>,
witness_2: Pat<'tcx>,
witness_3: Pat<'tcx>,
remainder: usize,
}
impl<'tcx> Uncovered<'tcx> {
pub fn new<'p>(
span: Span,
cx: &MatchCheckCtxt<'p, 'tcx>,
witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
) -> Self {
let witness_1 = witnesses.get(0).unwrap().to_pat(cx);
Self {
span,
count: witnesses.len(),
// Substitute dummy values if witnesses is smaller than 3. These will never be read.
witness_2: witnesses.get(1).map(|w| w.to_pat(cx)).unwrap_or_else(|| witness_1.clone()),
witness_3: witnesses.get(2).map(|w| w.to_pat(cx)).unwrap_or_else(|| witness_1.clone()),
witness_1,
remainder: witnesses.len().saturating_sub(3),
}
}
}
#[derive(Diagnostic)]
#[diag(mir_build_pattern_not_covered, code = "E0005")]
pub(crate) struct PatternNotCovered<'s, 'tcx> {
#[primary_span]
pub span: Span,
pub origin: &'s str,
#[subdiagnostic]
pub uncovered: Uncovered<'tcx>,
#[subdiagnostic]
pub inform: Option<Inform>,
#[subdiagnostic]
pub interpreted_as_const: Option<InterpretedAsConst>,
#[subdiagnostic]
pub adt_defined_here: Option<AdtDefinedHere<'tcx>>,
#[note(pattern_ty)]
pub _p: (),
pub pattern_ty: Ty<'tcx>,
#[subdiagnostic]
pub if_let_suggestion: Option<SuggestIfLet>,
#[subdiagnostic]
pub let_else_suggestion: Option<SuggestLetElse>,
#[subdiagnostic]
pub res_defined_here: Option<ResDefinedHere>,
}
#[derive(Subdiagnostic)]
#[note(mir_build_inform_irrefutable)]
#[note(mir_build_more_information)]
pub struct Inform;
pub struct AdtDefinedHere<'tcx> {
pub adt_def_span: Span,
pub ty: Ty<'tcx>,
pub variants: Vec<Variant>,
}
pub struct Variant {
pub span: Span,
}
impl<'tcx> AddToDiagnostic for AdtDefinedHere<'tcx> {
fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
where
F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
{
diag.set_arg("ty", self.ty);
let mut spans = MultiSpan::from(self.adt_def_span);
for Variant { span } in self.variants {
spans.push_span_label(span, rustc_errors::fluent::mir_build_variant_defined_here);
}
diag.span_note(spans, rustc_errors::fluent::mir_build_adt_defined_here);
}
}
#[derive(Subdiagnostic)]
#[label(mir_build_res_defined_here)]
pub struct ResDefinedHere {
#[primary_span]
pub def_span: Span,
pub res: Res,
}
#[derive(Subdiagnostic)]
#[suggestion(
mir_build_interpreted_as_const,
code = "{variable}_var",
applicability = "maybe-incorrect"
)]
#[label(mir_build_confused)]
pub struct InterpretedAsConst {
#[primary_span]
pub span: Span,
pub article: &'static str,
pub variable: String,
pub res: Res,
}
#[derive(Subdiagnostic)]
pub enum SuggestIfLet {
#[multipart_suggestion(mir_build_suggest_if_let, applicability = "has-placeholders")]
None {
#[suggestion_part(code = "if ")]
start_span: Span,
#[suggestion_part(code = " {{ todo!() }}")]
semi_span: Span,
count: usize,
},
#[multipart_suggestion(mir_build_suggest_if_let, applicability = "has-placeholders")]
One {
#[suggestion_part(code = "let {binding} = if ")]
start_span: Span,
#[suggestion_part(code = " {{ {binding} }} else {{ todo!() }}")]
end_span: Span,
binding: Ident,
count: usize,
},
#[multipart_suggestion(mir_build_suggest_if_let, applicability = "has-placeholders")]
More {
#[suggestion_part(code = "let ({bindings}) = if ")]
start_span: Span,
#[suggestion_part(code = " {{ ({bindings}) }} else {{ todo!() }}")]
end_span: Span,
bindings: String,
count: usize,
},
}
#[derive(Subdiagnostic)]
#[suggestion(
mir_build_suggest_let_else,
code = " else {{ todo!() }}",
applicability = "has-placeholders"
)]
pub struct SuggestLetElse {
#[primary_span]
pub end_span: Span,
pub count: usize,
}

1
compiler/rustc_mir_build/src/lib.rs
View file

@ -10,6 +10,7 @@
#![feature(let_chains)]
#![feature(min_specialization)]
#![feature(once_cell)]
#![feature(try_blocks)]
#![recursion_limit = "256"]
#[macro_use]

209
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -1,3 +1,8 @@
//#![allow(unused_imports, unused_variables)]
//#![warn(rustc::untranslatable_diagnostic)]
//#![warn(rustc::diagnostic_outside_of_impl)]
use super::deconstruct_pat::{Constructor, DeconstructedPat};
use super::usefulness::{
compute_match_usefulness, MatchArm, MatchCheckCtxt, Reachability, UsefulnessReport,
@ -9,8 +14,7 @@ use crate::errors::*;
use rustc_arena::TypedArena;
use rustc_ast::Mutability;
use rustc_errors::{
pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
MultiSpan,
struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
};
use rustc_hir as hir;
use rustc_hir::def::*;
@ -378,8 +382,8 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let pattern = self.lower_pattern(&mut cx, pat, &mut false);
let pattern_ty = pattern.ty();
let arms = vec![MatchArm { pat: pattern, hir_id: pat.hir_id, has_guard: false }];
let report = compute_match_usefulness(&cx, &arms, pat.hir_id, pattern_ty);
let arm = MatchArm { pat: pattern, hir_id: pat.hir_id, has_guard: false };
let report = compute_match_usefulness(&cx, &[arm], pat.hir_id, pattern_ty);
// Note: we ignore whether the pattern is unreachable (i.e. whether the type is empty). We
// only care about exhaustiveness here.
@ -390,145 +394,82 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
return;
}
let joined_patterns = joined_uncovered_patterns(&cx, &witnesses);
let mut bindings = vec![];
let mut err = struct_span_err!(
self.tcx.sess,
pat.span,
E0005,
"refutable pattern in {}: {} not covered",
origin,
joined_patterns
);
let suggest_if_let = match &pat.kind {
hir::PatKind::Path(hir::QPath::Resolved(None, path))
if path.segments.len() == 1 && path.segments[0].args.is_none() =>
let (inform, interpreted_as_const, res_defined_here, if_let_suggestion, let_else_suggestion) =
if let hir::PatKind::Path(hir::QPath::Resolved(
None,
hir::Path {
segments: &[hir::PathSegment { args: None, res, ident, .. }],
..
},
)) = &pat.kind
{
const_not_var(&mut err, cx.tcx, pat, path);
false
}
_ => {
pat.walk(&mut |pat: &hir::Pat<'_>| {
match pat.kind {
hir::PatKind::Binding(_, _, ident, _) => {
bindings.push(ident);
(
None,
Some(InterpretedAsConst {
span: pat.span,
article: res.article(),
variable: ident.to_string().to_lowercase(),
res,
}),
try {
ResDefinedHere {
def_span: cx.tcx.hir().res_span(res)?,
res,
}
_ => {}
},
None, None,
)
} else if let Some(span) = sp && self.tcx.sess.source_map().is_span_accessible(span) {
let mut bindings = vec![];
pat.walk_always(&mut |pat: &hir::Pat<'_>| {
if let hir::PatKind::Binding(_, _, ident, _) = pat.kind {
bindings.push(ident);
}
true
});
err.span_label(pat.span, pattern_not_covered_label(&witnesses, &joined_patterns));
true
}
};
if let (Some(span), true) = (sp, suggest_if_let) {
err.note(
"`let` bindings require an \"irrefutable pattern\", like a `struct` or \
an `enum` with only one variant",
);
if self.tcx.sess.source_map().is_span_accessible(span) {
let semi_span = span.shrink_to_hi().with_lo(span.hi() - BytePos(1));
let start_span = span.shrink_to_lo();
let end_span = semi_span.shrink_to_lo();
err.multipart_suggestion(
&format!(
"you might want to use `if let` to ignore the variant{} that {} matched",
pluralize!(witnesses.len()),
match witnesses.len() {
1 => "isn't",
_ => "aren't",
},
),
vec![
match &bindings[..] {
[] => (start_span, "if ".to_string()),
[binding] => (start_span, format!("let {} = if ", binding)),
bindings => (
start_span,
format!(
"let ({}) = if ",
bindings
.iter()
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ")
),
),
},
match &bindings[..] {
[] => (semi_span, " { todo!() }".to_string()),
[binding] => {
(end_span, format!(" {{ {} }} else {{ todo!() }}", binding))
}
bindings => (
end_span,
format!(
" {{ ({}) }} else {{ todo!() }}",
bindings
.iter()
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ")
),
),
},
],
Applicability::HasPlaceholders,
);
if !bindings.is_empty() {
err.span_suggestion_verbose(
semi_span.shrink_to_lo(),
&format!(
"alternatively, you might want to use \
let else to handle the variant{} that {} matched",
pluralize!(witnesses.len()),
match witnesses.len() {
1 => "isn't",
_ => "aren't",
},
),
" else { todo!() }",
Applicability::HasPlaceholders,
);
}
let count = witnesses.len();
let if_let = match *bindings {
[] => SuggestIfLet::None{start_span, semi_span, count},
[binding] => SuggestIfLet::One{start_span, end_span, count, binding },
_ => SuggestIfLet::More{start_span, end_span, count, bindings: bindings
.iter()
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ")},
};
let let_else = if bindings.is_empty() {None} else{Some( SuggestLetElse{end_span, count })};
(sp.map(|_|Inform), None, None, Some(if_let), let_else)
} else{
(sp.map(|_|Inform), None, None, None, None)
};
let adt_defined_here = try {
let ty = pattern_ty.peel_refs();
let ty::Adt(def, _) = ty.kind() else { None? };
let adt_def_span = cx.tcx.hir().get_if_local(def.did())?.ident()?.span;
let mut variants = vec![];
for span in maybe_point_at_variant(&cx, *def, witnesses.iter().take(5)) {
variants.push(Variant { span });
}
err.note(
"for more information, visit \
https://doc.rust-lang.org/book/ch18-02-refutability.html",
);
}
AdtDefinedHere { adt_def_span, ty, variants }
};
adt_defined_here(&cx, &mut err, pattern_ty, &witnesses);
err.note(&format!("the matched value is of type `{}`", pattern_ty));
err.emit();
}
}
/// A path pattern was interpreted as a constant, not a new variable.
/// This caused an irrefutable match failure in e.g. `let`.
fn const_not_var(err: &mut Diagnostic, tcx: TyCtxt<'_>, pat: &Pat<'_>, path: &hir::Path<'_>) {
let descr = path.res.descr();
err.span_label(
pat.span,
format!("interpreted as {} {} pattern, not a new variable", path.res.article(), descr,),
);
err.span_suggestion(
pat.span,
"introduce a variable instead",
format!("{}_var", path.segments[0].ident).to_lowercase(),
// Cannot use `MachineApplicable` as it's not really *always* correct
// because there may be such an identifier in scope or the user maybe
// really wanted to match against the constant. This is quite unlikely however.
Applicability::MaybeIncorrect,
);
if let Some(span) = tcx.hir().res_span(path.res) {
err.span_label(span, format!("{} defined here", descr));
self.tcx.sess.emit_err(PatternNotCovered {
span: pat.span,
origin,
uncovered: Uncovered::new(pat.span, &cx, witnesses),
inform,
interpreted_as_const,
_p: (),
pattern_ty,
if_let_suggestion,
let_else_suggestion,
res_defined_here,
adt_defined_here,
});
}
}

59
compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
View file

@ -292,7 +292,7 @@
use self::ArmType::*;
use self::Usefulness::*;
use super::deconstruct_pat::{Constructor, DeconstructedPat, Fields, SplitWildcard};
use crate::errors::NonExhaustiveOmittedPattern;
use crate::errors::{NonExhaustiveOmittedPattern, Uncovered};
use rustc_data_structures::captures::Captures;
@ -742,49 +742,6 @@ impl<'p, 'tcx> Witness<'p, 'tcx> {
}
}
/// Report that a match of a `non_exhaustive` enum marked with `non_exhaustive_omitted_patterns`
/// is not exhaustive enough.
///
/// NB: The partner lint for structs lives in `compiler/rustc_hir_analysis/src/check/pat.rs`.
fn lint_non_exhaustive_omitted_patterns<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
scrut_ty: Ty<'tcx>,
sp: Span,
hir_id: HirId,
witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
) {
let witness_1 = witnesses.get(0).unwrap().to_pat(cx);
cx.tcx.emit_spanned_lint(
NON_EXHAUSTIVE_OMITTED_PATTERNS,
hir_id,
sp,
NonExhaustiveOmittedPattern {
scrut_ty,
uncovered: sp,
count: witnesses.len(),
// Substitute dummy values if witnesses is smaller than 3.
witness_2: witnesses.get(1).map(|w| w.to_pat(cx)).unwrap_or_else(|| witness_1.clone()),
witness_3: witnesses.get(2).map(|w| w.to_pat(cx)).unwrap_or_else(|| witness_1.clone()),
witness_1,
},
);
/*
cx.tcx.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS, hir_id, sp, "some variants are not matched explicitly", |lint| {
let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
lint.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns));
lint.help(
"ensure that all variants are matched explicitly by adding the suggested match arms",
);
lint.note(&format!(
"the matched value is of type `{}` and the `non_exhaustive_omitted_patterns` attribute was found",
scrut_ty,
));
lint
});
*/
}
/// Algorithm from <http://moscova.inria.fr/~maranget/papers/warn/index.html>.
/// The algorithm from the paper has been modified to correctly handle empty
/// types. The changes are:
@ -930,7 +887,19 @@ fn is_useful<'p, 'tcx>(
.collect::<Vec<_>>()
};
lint_non_exhaustive_omitted_patterns(pcx.cx, pcx.ty, pcx.span, hir_id, patterns);
// Report that a match of a `non_exhaustive` enum marked with `non_exhaustive_omitted_patterns`
// is not exhaustive enough.
//
// NB: The partner lint for structs lives in `compiler/rustc_hir_analysis/src/check/pat.rs`.
cx.tcx.emit_spanned_lint(
NON_EXHAUSTIVE_OMITTED_PATTERNS,
hir_id,
pcx.span,
NonExhaustiveOmittedPattern {
scrut_ty: pcx.ty,
uncovered: Uncovered::new(pcx.span, pcx.cx, patterns),
},
);
}
ret.extend(usefulness);